The hardware programming guide recommends to clear all registers on
first initialization, through separate field in BWMON_CLEAR register.

This makes sense in general but especially if driver is rebound to avoid
spurious/early interrupts.

Cc: Rajendra Nayak <quic_rjendra@quicinc.com>
Cc: Sibi Sankar <quic_sibis@quicinc.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Tested-by: Steev Klimaszewski <steev@kali.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220728113748.170548-6-krzysztof.kozlowski@linaro.org